Covariant spin tensors in meson spectroscopy

It is shown that the decay amplitude of a particle with spin to one spinless meson and a resonance with spin can be expressed in a general and compact form using the covariant tensor (also named Rarita-Schwinger) formalism. The identity of this formalism with the covariant helicity formalism recently proposed by Chung is shown. Many angular distributions are derived, showing that in some cases there are large differences with the distributions calculated with noncovariant (Zemach or helicity) amplitudes. These differences are shown in detail for some Dalitz plots relative to the annihilation pp¯→πππ at low energy. Although the worked examples refer to binary decays with spins ≤2 only, the covariant tensor formalism is presented in a general form to permit its extension to more complicated cases.